I am not wiki-san but i will try to answer from my shallow pool of knowledge, fats should be more your body's energy storage, meaning it acts as a reservoir of energy. It releases twice as much energy compare to carbohydrates and protein(not sure bout this).
Your body tend to rely on immediate energy source when it requires, the simplest form of obtaining instant energy is through carbohydrates. When it run out of source from carbohydrates then only it will straight pulling out from the reservoir - fats.
For the 15mins thingy, i am not too sure. Wait wiki-san to clarrified on it xD
@clark
thanks for the link but i have read it before edi.
Speaking of McD, i dont quite like to eat them but they are damn convenient with their drive through service. I used to eat it quite often because it's the only food you can buy along MRR2 and eat when you drive lol
hehe thanks tengster i will try to look out for it, spaghetti yum yum
strangely i like to eat it in Chinese cooking style, mee soup xD. hate pasta sauce.
p/s wikisan posted before me